[0001] The present invention relates to a lifting system for concrete components and more particularly to a lifting anchor for quick release from the component.

[0002] One commonly used technique for repairing damage to roadways constructed of poured concrete is to cut out the damaged section and to replace it with a precast panel of the same dimensions. Usually the panel will be cast offsite, trucked to the site and then lifted into position. Typically the panel, which may weigh several tons, is lifted by the use of lifting anchors screwed into threaded inserts cast into the panel during its manufacture. Conventionally, the threaded inserts are in the form of internally-threaded collars which, after casting, open onto the upper face of the panel to receive the lifting anchors. For the several separate lifting operations likely to be involved between casting and laying of the slab in position, and likely involving storage of several panels in stacked relation and transportation of several panels in stacked relation, the lifting anchors will usually be required to be installed and removed several times. This can be quite a time-consuming and laborious operation as the thread length on the insert and which corresponds to the thread length of a threaded stem of the anchor runs for almost the full thickness of the panel.

[0003] At their lower ends the threaded inserts, although open, abut against a metal jacking plate, one for each insert, set into the underside of the panel during casting. After laying of the panel in position and removal of the lifting anchors, jacking rods are screwed into the inserts to engage the jacking plates which are in contact with compacted ground beneath the panel, in order to raise the panel so that it is set level with the surrounding roadway. During manufacture of the panel, grout holes are cast through the thickness of the panel at different locations over the surface of the panel and when the panel has been jacked into a position in which it is level with the surrounding roadway, concrete grout is injected through the grout holes to the underside of the panel in order to fill the void between the underside of the panel and the underlying ground surface. The jacking rods are removed from the threaded inserts after the grout has cured sufficiently to support the weight of the panel. As with the lifting anchors, because threaded engagement between the jacking rods and inserts occurs over a substantial thread length, it is a time-consuming and laborious operation to insert and remove the jacking rods. [0004] The present invention in one aspect provides a lifting system which enables quick insertion and release of lifting anchors into a panel such as a repair panel discussed above, and also quick insertion and release of subsequent jacking rods.

[0005] According to the present invention there is provided a lifting system for a concrete component, comprising a void former for incorporation into the component during casting thereof, the void former providing a passage to receive a locking stem of a lifting anchor assembly following casting, the void former providing a void within the component shaped for locking engagement with a locking pin of the locking stem by rotation of the pin following insertion whereby to lock the stem within the void to permit lifting load to be applied, the void former also including a jacking plate and associated threaded structure for receiving a threaded jacking rod inserted through the void former after removal of the lifting anchor assembly to permit jacking of the component from underlying structure.

[0006] Although the lifting system of the invention has particular utility in conjunction with a jacking system for use with roadway repair panels, the lifting system by virtue of its quick insertion and release characteristics also has utility in other aspects of concrete lifting of components where jacking is not required.

[0007] Accordingly another aspect of the invention provides a lifting system for a concrete component, comprising a void former for incorporation into the component during casting thereof, the void former providing a passage to receive a locking stem of a lifting anchor assembly following casting, the void former providing a void within the component shaped for locking engagement with a locking pin of the locking stem by rotation of the pin following insertion whereby to lock the stem within the void to permit lifting load to be applied, wherein the locking pin includes at least one locking lug movable into a locking condition within the void former upon rotation of the pin, the locking stem also including fixed structure located within the void former and engageable with the lug by axial displacement of the pin in order to provide a positive lock against rotation of the pin out of its locking condition.

[0008] The present invention also provides a void former configured for use in lifting systems as defined above. [0009] An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which:

[0010] Figure 1 shows a void former assembly of a lifting system in accordance with the preferred embodiments;

[0011] Figure 2 shows the individual components of the void former assembly in exploded form;

[0012] Figure 3 shows a lifting anchor assembly engageable into a void formed by the void former assembly, the lifting anchor assembly being shown in a configuration in which a locking pin thereof is in a condition to enable insertion of a locking stem into the void;

[0013] Figure 4 shows the relation between the lifting anchor assembly and void former assembly for insertion of the locking stem;

[0014] Figure 5 shows the lifting anchor assembly in a condition in which the locking pin has been rotated to an engaged locking position;

[0015] Figure 6 shows the detailed structure of the lifting anchor assembly in the insertion conditions of Figures 3 and 4;

[0016] Figure 6A shows an enlarged detail of Figure 6;

[0017] Figure 7 shows the detailed structure of the lifting anchor assembly in the engaged locking condition of Figure 5; and

[0018] Figure 7A shows an enlarged detail of Figure 7.

[0019] With initial reference to Figures 1 and 2 the quick release lifting system of the preferred embodiment of the invention comprises a void former assembly comprising a tubular main body 2 coupled at its lower end with a base formed by upper and lower shallow shells 4, 6 of rectangular form for housing components of a jacking system used to subsequently level a panel as discussed earlier. The tubular main body 2 is of generally cylindrical form but with two inset channels 8 of approximately dovetail section at opposite sides. An external wall 10 closes each channel 8 at its lower end. The end wall 10 which is also of dovetail section is upwardly inclined and has a curved outer edge which corresponds to the curvature of the curved parts of the tubular body 2. A circular plate 12 at the top of the tubular body 2 is formed with an aperture 14 of a shape which corresponds to the internal cross-section of the tubular body 2. A removable cap 16 is fitted to the plate 12 and is retained within a peripheral lip thereof. For casting into the panel, the void former is set with its base on the casting bed, and following casting the cap 16 of the void former will be substantially flush with the upper surface of the cast panel.

[0020] With reference now to Figures 3 to 5 a lifting anchor assembly 20 comprises a main stem 22 which is engaged within the tubular body 2 of the void former after removal of the cap 16. The stem 22 consists of a central rotatable locking pin 24 having at its lower end opposed locking lugs 26 of dovetail shape corresponding to that of the cross-section of the two channels 8 in the void former. The pin 24 is located between two fixed annular segments 28. It will be seen from the drawings that the overall configuration of the stem 22 formed by the rotary pin 24 and fixed outer segments 28 substantially corresponds to that of the tubular body 2 of the void former. As will be described in more detail shortly, the pin 24 is rotatable through 90° from a position in which its locking lugs 26 are aligned with the segments 28 (see Figure 3) whereby the stem 22 can be inserted into the interior of the void former via the aperture 14 in the plate 12 (see Figure 4) and a locking position displaced through 90° in which the locking lugs 26 are between the segments 28 (see Figure 5).

[0021] The main stem 22 is carried by an upper body 30 the lower edge of which sits within the circular plate 12 when the anchor is installed to the panel. A lifting shackle plate 32 with lifting eye 33 for coupling to a lifting clutch is pivotally mounted to the body 30 for movement between a position in which it extends generally horizontally and which is assumed during installation of the lifting anchor assembly into the panel, and a generally vertical position which it assumes during lifting. The detailed internal structure of the upper body 30 is shown in Figures 6 and 7 but with an external cover of the body omitted for clarity of illustration. As shown in these Figures, the fixed segments 28 of the main stem 22 are fixed to the body 30 and the locking pin 24 is rotatably mounted in the body 30 and is connected at its upper end to an upper handle 34. A locking collar 36 is mounted to an enlarged upper end of the locking pin 24 beneath the handle 34. A compression spring 40 mounted on the upper part of the locking pin 24 between a lower part of the upper body 30 and the collar 36 applies an upward bias to the locking pin 24 and hence to the handle 34 attached thereto.

[0022] When the locking pin 24 and its associated handle 34 are in the rotational position for insertion of the stem 22 into the void former, the locking lugs 26 are aligned with the fixed segments 28 and in that condition the locking pin 24 and its associated handle are in a lowered position in which the locking lugs 26 are held against the lower edge of the segments 28 under the effect of the bias of the compression spring 40 (see Figure 6). When, following insertion, the handle 34 is rotated through 90° to pivot the pin 24 into its locking condition between the segments 28, under the effect of the compression spring 40, the pin 24 and associated handle 34 lift so that the locking lugs 26 will lie within the slots defined between the opposed edges of the two segments 28 whereby the pin is 24 positively locked by those edges against rotation out of that locking condition (see Figure 7). The upwards movement which occurs to lock the pin is only a few millimeters and is limited by the configuration of the void former and in particular the lower end wall 10 of each of the two external channels 8. It is in this mode that lifting load can be applied.

[0023] The shackle plate 32 is journalled in the upper body 30 by lateral trunions 32a, the ends of which are shaped to define locking flats 32b as clearly shown in Figures 6 and 7. The locking flats 32b lie beneath the collar 36. The flats are so configured that in the rotational position of the pin 24 which it adopts for insertion into the void former and which is a lowered position of the pin, the locking flats 32b are engaged by the underside of the collar 36 whereby the lifting eye is locked by the collar in its horizontal configuration (see Figures 6 and 6A). In the locked condition of the locking pin 24 in which the pin and hence collar and handle are raised relative to the insertion position, the underside of the collar 36 is now raised clear of the locking flats 32b (see Figures 7 and 7A) whereby the shackle plate 32 can now be rotated into its generally vertical lifting configuration. This provides a significant safety feature as it ensures that the shackle plate cannot be moved to its lifting configuration unless the locking pin 24 is in its locked configuration.

[0024] Although identification as to whether the locking pin 24 is in its insertion or locked position can be visually attained by reference to the rotational position of the handle 34, it is preferred to additionally incorporate an indicator readily visible from a more remote distance to particularly show that the pin it in its engaged locking condition. In the insertion position the handle 34 lies relatively close to an upper cover 30a of the upper body 30 (see Figures 3 and 4). In the engaged locking condition, the handle 34 and adjacent section of the upper part of the pin 24 is raised relative to the upper cover 30a and that part 24a of the pin which is now exposed is coloured in a readily identifiable colour, such as green as shown in Figure 5, to provide a further visual identification that the lifting system is in a locked condition within the panel and hence in a "safe" condition for lifting.

[0025] As mentioned previously, the base of the void former assembly also includes components of the jacking system used for leveling the panel after installation. A jacking plate 50, preferably a steel plate, is housed within a void within the two shells 4, 6 of the base and is not exposed to the surrounding concrete after pouring. As such the plate will be free to displace when jacking force is applied. The upper shell 4 also houses a nut 52 which is located above and adjacent to the jacking plate 50 in alignment with the axis of the tubular body 2 of the void former. After removal of the lifting anchor assembly following lowering of the panel into place within the roadway, a threaded jacking rod is inserted through the void former into engagement with the nut 52 and after only a few turns, perhaps just one or two turns, it will engage the jacking plate 50 to start raising the panel into its final leveled configuration. While this is fundamentally the same process as that previously described, it will be understood that whereas in the earlier arrangement in which the threaded insert extended substantially the full depth of the panel many turns of the jacking rod were required before the jacking action could commence, and subsequently many turns were required to remove the jacking rod after completion of the setting operation, with the incorporation of the nut 52 towards the lower end of the void former immediately adjacent the jacking plate that action can be accomplished much more quickly.

[0026] Although the embodiment typically described has been designed for the dual functions of providing a quick release lifting system combined with a jacking system also for quick release, an embodiment similar to that described but without the incorporation of the jacking system could provide a quick release lifting system for other precast concrete components when it is required to provide removable lifting anchors rather than cast-in lifting anchors as would typically be used in building construction involving the use of face lift or edge lift precast wall panels. [0027] The embodiment has been described by way of example only and modifications are possible within the scope of the invention.